A coenzyme Q is an essential component widely distributed in living bodies from bacteria to mammals. In humans, it is known that the main component thereof is coenzyme Q10 whose coenzyme Q side chain has 10 repeating structures. Coenzyme Q10 is a physiological component occurring as an electron transfer system constituent in mitochondria in cells of living bodies and performs its function as a transmitter component in the electron transfer system by repeatedly undergoing oxidation and reduction in living bodies. The coenzyme Q is known to show energy producing, membrane stabilizing and antioxidant activities in living bodies and is in wide use. Among coenzyme Q10 species, oxidized Q10 (ubiquinone or ubidecarenone) is used as a drug for congestive heart failure and thus is known to effectively act on the heart. As for its effects, improvement in oxygen utilization efficiency in heart muscle, activation of ATP production in heart muscle, and improvement in heart function, and the like, have been reported. In the fields other than the pharmaceutical field, effects as a nutrient or nutrient supplement, like those of vitamins, have been reported. A tissue metabolism activating composition comprising a mixture of ubiquinone and a dried yeast powder (Japanese Kokai Publication Sho62-59208), improvements in symptoms of myasthenia gravis by a composition comprising ubiquinone (Japanese Kokai Publication Sho52-99220) and an erythrocyte increasing effect of a composition comprising ubiquinone (Japanese Kokai Publication Sho52-99222, and the like, have also been reported. Furthermore, a fatigue relieving effect has been reported (Japanese Kokai Publication Hei07-330584; Japanese Kokai Publication Hei07-330593; Japanese Kokai Publication Hei10-287560).
As regards reduced coenzyme Q10, unlike the oxidized form, there is no report about the utility thereof. This is because reduced coenzyme Q10 is readily susceptible to air oxidation and, therefore, cannot have been evaluated for utility. One of the reasons why reduced coenzyme Q10 has not been evaluated for utility is that it is generally known that even oxidized coenzyme Q10 is administered, it undergoes reduction in living bodies and this results in an increase in reduced coenzyme Q10 level and it has been considered that oxidized coenzyme Q10 and reduced coenzyme Q10 should be equal in efficacy to living bodies. Previously, we disclosed that the oral absorbability of a coenzyme Q is increased by the coexistence of a reduced coenzyme Q as compared with the corresponding oxidized coenzyme Q alone (Japanese Kokai Publication Hei10-109933) and showed that the utilization of a reduced coenzyme Q is effective in increasing the oral absorbability. This composition gave a maximum plasma concentration (Cmax) about twice higher as compared with the oxidized coenzyme Q alone. However, the rate of disappearance thereof is rapid and no improvement in maintenance of high concentration of coenzyme Q in blood was observed.
It is well known from the experience in drug development research works, and the like, that, in the case of such a hydrophobic substance as coenzymes Q, not only an increase in Cmax but also an improvement in maintenance of high concentration of coenzyme Q in blood (AUC) is generally desirable for effective manifestation of an effect thereof in living bodies, whatever the effect is. Thus, although an increase in Cmax is indeed an important factor for effectively using substances not so strong in effects, such as coenzymes Q, various effects can be expected when a high blood level can be maintained. For example, if a coenzyme Q maintains its high concentration in blood for a prolonged period of time, its antioxidant activity will be maintained at a high level and it can be expected for the frequency of occurrence of arteriosclerosis, diabetic complications, cerebral diseases, renal diseases and like diseases caused by oxidative stresses in blood to be efficiently decreased. Further, while coenzyme Q10 is thought to migrate to various tissues or organs and activate the energy production or enhance the antioxidant activity in respective organs to produce various biological effects, the maintenance of high concentration of coenzyme Q10 in blood for a prolonged period of time can be expected to increase the probability of its migration to various tissues or organs, since its migration to respective tissues or organs takes place through blood. Therefore, for increasing the probability of manifestation of a number of effects of coenzyme Q10, it is necessary to maintain its blood concentration at high levels.